In recent years, the development of the Internet has made it possible for people to access large quantities of information in real time and to handle large quantities of information. Information is transmitted by copper wire, optical fiber and wirelessly, but optical fiber is particularly superior for sending large volumes of information at high speeds. In the future, optical fiber is expected to be installed in each home.
However, because at the terminal end information is processed using electric signals, not optical signals, an optical module has to be used between an optical fiber and a terminal in order to connect the optical fiber to the terminal. An optical module is a device that converts optical signals received from the optical fiber to electric signals and supplies the electric signals to the terminal, and converts electric signals from the terminal to optical signals that are supplied to the optical fiber. In the prior art, various types of optical module have been proposed.
FIG. 12 is a cross-sectional diagram showing the structure of a conventional optical module 10 described in Japanese Utility Model Registration No. 3,095,902. The optical module 10 includes a main housing 12, an optical fiber 14 supported by the optical module 10, a light-emitting component 16, a light-receiving component 18, a filter support member 20 provided in the main housing 12, and an optical filter 22 supported by the filter support member 20.
In the optical module 10 shown in FIG. 12, the optical fiber 14 and light-receiving component 16 are disposed in a straight line and the light-receiving component 18 is disposed at an angle of 90 degrees to the straight line. The optical filter 22 reflects received light 14a supplied from the optical fiber 14 and transmits transmitted light 16a produced by the light-emitting component 16. The filter support member 20 supports the optical filter 22 at an angle of 45 degrees to the straight line. Thus, received light 14a from the optical fiber 14 is reflected by the optical filter 22 to fall incident on the light-receiving component 18, and transmitted light 16a from the light-emitting component 16 is transmitted by the optical filter 22 to the optical fiber 14.
This arrangement enables an optical signal received from the optical fiber 14 to be converted to an electric signal and supplied to the terminal, and an electric signal provided from the terminal to be converted to an optical signal and supplied to the optical fiber 14, thereby enabling bi-directional communication between terminals using optical signals.
However, in the case of the above optical module 10, the transmitted light 16a produced by the light-emitting component 16 can stray and scatter within the main housing 12, and if this scattered light reaches the light-receiving component 18, it can result in noise, with respect to the received signal. One way of resolving this problem is to provide another optical filter at the light-receiving component 18 end to block stray light.
However, the provision of another member to support the optical filter further increases the number of parts. Moreover, an increase in the number of parts such as the filter support members, which are small and irregular in shape, makes the manufacturing process more complicated and increases the cost of the products.